The playing of movies and video is today accomplished with rather old technology. The primary storage media is analog tape, such as VHS recorders/players, and extends up to the very high quality and very expensive D1 VTR's used by television studios and broadcasters. There are many problems with this technology. A few such problems include: the manual labor required to load the tapes, the wear and tear on the mechanical units, tape head, and the tape itself, and also the expense. One significant limitation that troubles Broadcast Stations is that the VTRs can only perform one function at a time, sequentially. Each tape unit costs from $75,000 to $150,000.
TV stations want to increase their revenues from commercials, which are nothing more than short movies, by inserting special commercials into their standard programs and thereby targeting each city as a separate market. This is a difficult task with tape technology, even with the very expensive Digital D1 tape systems or tape robots.
Traditional methods of delivery of multimedia data to end users fall into two categories: 1) broadcast industry methods and 2) computer industry methods. Broadcast methods (including motion picture, cable, television network, and record industries) generally provide storage in the form of analog or digitally recorded tape. The playing of tapes causes isochronous data streams to be generated which are then moved through broadcast industry equipment to the end user. Computer methods generally provide storage in the form of disks, or disks augmented with tape, and record data in compressed digital formats such as DVI, JPEG and MPEG. On request, computers deliver non-isochronous data streams to the end user, where hardware buffers and special application code smooths the data streams to enable continuous viewing or listening.
Video tape subsystems have traditionally exhibited a cost advantage over computer disk subsystems due to the cost of the storage media. However, video tape subsystems have the disadvantages of tape management, access latency, and relatively low reliability. These disadvantages are increasingly significant as computer storage costs have dropped, in combination with the advent of the real-time digital compression/decompression techniques.
Though computer subsystems have exhibited compounding cost/performance improvements, they are not generally considered to be "video friendly". Computers interface primarily to workstations and other computer terminals with interfaces and protocols that are termed "non-isochronous". To assure smooth (isochronous) delivery of multimedia data to the end user, computer systems require special application code and large buffers to overcome inherent weaknesses in their traditional communication methods. Also, computers are not video friendly in that they lack compatible interfaces to equipment in the multimedia industry which handle isochronous data streams and switch among them with a high degree of accuracy.
With the introduction of the use of computers to compress and store video material in digital format, a revolution has begun in several major industries such as television broadcasting, movie studio production, "Video on Demand" over telephone lines, pay-per-view movies in hotels, etc. Compression technology has progressed to the point where acceptable results can be achieved with compression ratios of 100.times. to 180.times.. Such compression ratios make random access disk technology an attractive alternative to prior art tape systems.
With an ability to random access digital disk data and the very high bandwidth of disk systems, the required system function and performance is within the performance, hardware cost, and expendability of disk technology. In the past, the use of disk files to store video or movies was never really a consideration because of the cost of storage. That cost has seen significant reductions in the recent past.
For the many new emerging markets that utilize compressed video data, using MPEG standards, there are several ways in which video data can be stored in a cost effective manner. This invention provides a hierarchical solution to many different performance requirements and results in a modular systems approach that can be customized to meet market requirements.